Ballistic polycrystalline mining tool and method for making the same

ABSTRACT

A cutting element for a mining or drilling tool provides a body that provides a recess for receiving a ballistic insert. The ballistic insert provides a top portion having a shape characterized by a first radius (R1) and a second radius (R2), and R1 and R2 have a tangential relationship. A sleeve may be positioned on the body to protect the body from erosion.

RELATED APPLICATIONS

This application claims the benefit of Chinese Patent Application No. 201310078101.6, filed on Mar. 12, 2013 which is incorporated herein by reference.

FIELD OF THE INVENTION

This invention relates to a mining tool and method. More particularly, to a mining tool or method that utilizes polycrystalline cutting elements.

BACKGROUND OF INVENTION

Cutting elements are used in earth boring bits or the like for drilling and excavating earth formations. Degradation of cutting structure during the excavation process often leads to down time of expensive machinery used in underground mining or road repair applications. Consequently, extension of life of cutting structures is very important to performance of mining tools. U.S. Pat. Nos. 6,102,486 and 4,944,559 describe body of tool that have as steel body in which hard material such as cemented carbide cutting structure is embedded. Attempts to apply super hard material such as polycrystalline diamond on the cutting tip is described in U.S. Pat. No. 8,136,887 on a substantially conical surface with aside forming a 35 to 55 degree angle with the central axis of the tool and having apex of 0.050 to 0.125 inch radius.

The performance of such super hard conical tools has had limited viability since the outer layer tends to fracture prematurely due to the geometry and composition of the working layer, which makes it highly brittle. These tools have not been very cost effective in mining and concrete milling applications.

SUMMARY OF THE INVENTION

In one embodiment, a cutting element includes a ballistic-shaped insert. In some embodiment, the ballistic-shaped insert may provide a substrate comprising an end surface that is attached to two layers of a tough grade of polycrystalline diamond (PCD) material layers. The PCD material layer is formed by mixing cobalt, tungsten carbide and diamond crystals together with a sandwich layer that acts as shock absorbing layer. The sandwich layer may be formed from a mixture of diamond, cobalt or carbide of elements of periodic table Group IV and/or V, or a combination thereof. In some embodiments, the sandwich layer may include cubic boron nitride (CBN) in addition to the materials previously mentioned. The various layers of the ballistic-shaped insert may be secured on a carbide or cermet substrate. In another embodiment, the ballistic-shaped insert may be a mixture of polycrystalline diamond and cubic boron nitride. In other embodiments, the ballistic-shaped insert is polycrystalline diamond (PCD), cubic boron nitride (CBN), cobalt, carbide, cobalt or carbides of Group IV and/or Group V, tungsten, or a combination thereof. In some embodiments, the ballistic-shaped insert is secured to a body having an opening to receive the ballistic-shaped insert. In some embodiments, a sleeve may be positioned on the body to protect the steel body from erosion and wear. In some embodiments, the body may be a steel body. In some embodiments, the sleeve may be a carbide.

In some embodiments, a top portion of the ballistic-shaped insert may be defined by radius R1 and R2. In some embodiments, R1 and R2 may have a tangential relationship. In some embodiments, the ratio of R1 to R2 (R1/R2) is equal to or greater than 18. In other embodiments, the ratio of R1 to R2 is between approximately 18 to 23. In some embodiments, R2 is between approximately 0.02 to 0.30 inches or 0.5 to 7.6 m. In some embodiments, R1 is between approximately 1.2 to 10 inches or 30.5 to 254 mm. In some embodiments, the ratio of R1 to R2 is 4 or greater.

The foregoing has outlined rather broadly various features of the present disclosure in order that the detailed description that follows may be better understood. Additional features and advantages of the disclosure will be described hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present disclosure, and the advantages thereof, reference is now made to the following descriptions to be taken in conjunction with the accompanying drawings describing specific embodiments of the disclosure, wherein:

FIGS. 1A-1D are an illustrative implementation of a cutting element with a ballistic insert, steel body, and sleeve;

FIG. 2 is an illustrative implementation of a finite element model showing stress on the insert of a ballistic PCD insert;

FIG. 3 is an illustrative implementation of a finite element model showing stress on the insert of a conical PCD insert;

FIGS. 4A-4B are an illustrative implementation of a ballistic insert with a radii R1 and R2;

FIGS. 5A-5B are an illustrative implementation of a ballistic insert with a concave apex; and

FIGS. 6A-6B are an illustrative implementation of a ballistic insert with a round top.

DETAILED DESCRIPTION

Refer now to the drawings wherein depicted elements are not necessarily shown to scale and wherein like or similar elements are designated by the same reference numeral through the several views.

Referring to the drawings in general, it will be understood that the illustrations are for the purpose of describing particular implementations of the disclosure and are not intended to be limiting thereto. While most of the terms used herein will be recognizable to those of ordinary skill in the art, it should be understood that when not explicitly defined, terms should be interpreted as adopting a meaning presently accepted by those of ordinary skill in the art.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only, and are not restrictive of the invention, as claimed. In this application, the use of the singular includes the plural, the word “a” or “an” means “at least one”, and the use of “or” means “and/or”, unless specifically stated otherwise. Furthermore, the use of the term “including”, as well as other forms, such as “includes” and “included”, is not limiting. Also, terms such as “element” or “component” encompass both elements or components comprising one unit and elements or components that comprise more than one unit unless specifically stated otherwise.

Improved mining tools and methods are discussed herein. Mining tools utilized to drill and excavate earth formations may provide components that abrade, impact, shear, and/or the like a desired region of a formation. For example, a mining tool may be used for removal of earth formations, asphalt, concrete and/or surface removal. A mining tool may comprise at least one tooling element. These mining tools may provide a tooling element that rotates and/or impacts the formation, such as a bit or the like. The tooling element may provide at least one cutting element that is designed to abrade, impact, shear, and/or the like.

A tooling element may provide a body that has several recesses for receiving one or more cutting elements. FIGS. 1A-1D are an illustrative implementation of a cutting element 200 with a ballistic insert 210, body 220, and sleeve 230. A cutting element 200 for use in a bit or the like may provide a cutting layer formed from tough grade material(s) that are able to withstand the stresses imparted on the cutting element during mining or drilling. Ballistic insert 210 may be shaped to withstand stresses exerted during mining or drilling. Steel body 220 may provide an opening or recess for receiving ballistic insert 210. In some embodiments, ballistic insert 210 may be brazed to the steel body 220. A sleeve 230 may be positioned on the body 220 and ballistic insert 210 to protect a portion of the body from erosion. In some embodiments, sleeve 230 may be bonded to the body 220 with a high strength epoxy. In some embodiments, the cutting layer surface may be a polycrystalline diamond (PCD) characterized by a mixture of diamond crystals, cobalt or carbides of group IV and/or group V and tungsten carbide particles; a cubic boron nitride (CBN) mixture; or a combination thereof.

In an exemplary embodiment, a cutting element 200 is provided where ballistic insert 210 made of PCD is used to form a cutting layer. In the exemplary embodiment, the PCD material extends along a section of the ballistic insert 210 so as to make contact with the earth formations during mining or drilling. The various embodiments of ballistic inserts discussed herein may be formed from diamond crystals, a catalyst for forming diamond crystals, a group IV and/or V, cobalt, carbide, tungsten carbide, cubic boron nitride (CBN), combinations thereof, and/or any other suitably tough material(s). As non-limiting example, the ballistic insert may be made from a mixture of diamond crystals and CBN. Another non-limiting example is a ballistic insert that provides a mixture of diamond and catalysts, such as cobalt, which is bonded to a tungsten carbide substrate. In some embodiments, the ballistic insert may be a solid body of material(s), and, in other embodiments, the ballistic insert may include two or more layers. In some embodiments, a sandwich layer may be provided as a shock absorbing layer. In some embodiments, the sandwich layer may comprise a mixture of diamond, a catalyst for forming diamond crystals, a group IV or group V material, cobalt, carbide, tungsten carbide, cubic boron nitride (CBN), or a combination thereof. In some embodiments, the sandwich layer may comprise 70-80% (by weight) carbide, 0-5% cobalt, and 8-18% diamond. Further, in another embodiment, the sandwich layer may provide material percentages in the same ranges and may also include 0-3.5% (by weight) CBN 0-3.5.

In some embodiments, ballistic inserts may comprise a single solid body made of one or more material(s) or a solid insert. For example, in an exemplary embodiment, a ballistic insert may be a solid PCD, as opposed to a PCD bonded to a carbide substrate. In other embodiments, the solid body may be CBN, a mixture of PCD and cobalt, or a mixture of CBN and PCD. In some embodiments, the ballistic inserts may be thermally stable or treated to prevent damage from thermal expansion. For example, a PCD and catalyst mixture may be acid leached to remove catalyst material that expands at a greater rate than the PCD when heated. In some embodiments, a ballistic insert may comprise multiple layers of materials, such as diamond and catalyst layers bonded to a tungsten carbide substrate. In some embodiments, ballistic inserts may be graded to provide different concentrations of the material(s). For example, a cutting layer provided by a top layer of a ballistic insert may be the toughest layer with a high ratio of diamond crystals to catalyst, whereas subsequent layers of diamond and catalyst below the top cutting layer have increasing percentages of catalyst.

Body 220 of the cutting element may provide a bottom portion shaped to allow the body to be secured to a mining tool. A braze material may be utilized to secure the ballistic insert 210 and body 220 together. Body 220 may be steel, titanium and its alloys, cermets or any other suitable material. In some embodiments, body 220 may also have openings or grooves positioned at specific locations that are subject to high stresses. Segments of hard materials, such as cemented carbide, segments of diamond and CBN, boron carbide, silicon carbide segments, may be either brazed or bonded by high temperature epoxy into the openings. To protect body 220 from erosion, sleeve 230 is secured onto ballistic insert 210 and body 220. Sleeve 230 may have a thickness between approximately 0.040 to 0.500 inch or approximately 0.1 mm to 12.7 mm. Sleeve 230 may be a cemented carbide or any other suitable material. In some embodiments, the sleeve 230 is bonded to the body 220 by means of high strength epoxy having strength of approximately 5000 psi or greater. The epoxy may be a high temperature epoxy. Alternatively, cemented carbide sleeve can be bonded to the body 220 by means of braze material. In some embodiments, the sleeve may be conically shaped. However, in other embodiments, the sleeve may have any shape.

FIG. 2 is an illustrative embodiment of a finite element model of a ballistic PCD insert. FIG. 3 is an illustrative embodiment of a finite element model of a conical PCD insert. The conical PCD insert may experience 14.4×10⁶ PSI of stress (von Mises), whereas the ballistic PCD dip may experience 610×10³ PSI of stress (von Mises). In the embodiments above, the ballistic insert reduces stresses by a factor of 10 over the conical insert.

FIG. 4A-4B are an illustrative embodiment of a ballistic insert 300. Ballistic insert 300 provides a base 310 and a top portion 320. In some embodiments, top portion 320 may be bonded to base 310 and the interface between base 310 and top portion 320 may be planar. Base 310 provides a portion of ballistic insert 300 that may be secured by a body. In the embodiment shown, base 310 may be a cylindrically-shaped body with a diameter (D) and a base height (BH). However, in other embodiments, the base 310 may be any other suitable shape. Top portion 320 provides a portion of ballistic insert 300 that may contact a formation during mining or drilling. While some mining tools utilize conically-shaped inserts, it is apparent from FIG. 4 that such conical inserts are subjected to significant stress. In order to reduce stress, top portion 320 is curved like a ballistic projectile, such as a bullet. In some embodiments, a ballistic insert 300 may provide a top portion defined by two radii, R1 and R2. Top portion 320 has a total height (H). H1 defines the height of a first section comprising the tip of top portion 320, and the first section is defined by radius R2. H2 defines the height of a second section of top portion 320 below the tip or first section, and the second section is defined by radius R1. It should be apparent that a circle or sphere providing a radius R2 would have a center positioned along the central axis of ballistic insert 300. The total height (H) of top portion 320 is equal to the sum of H1 and H2. R1 and R2 form a tangential relationship with one another. In other words, where R1 and R2 meet, R1 and R2 share the same tangent line. It should be recognized that the total height (H) of the top portion 320 is large in comparison to other prior art devices. In some embodiments, the total height (H) is 1 inch or greater. In some embodiments, the ratio of R1 to R2 is 4 or greater. In other embodiments, the ratio of R1 to R2 is 18 or greater. In other embodiments, the ratio of R1 to R2 (R1/R2) is between 18 to 23. In some embodiments, top portion 320 has a radius R2 between approximately 0.020 to 0.300 inches (or approximately 0.5 to 7.6 mm). In some embodiments, top portion 320 has a radius R1 between approximately 1.2 to 10 inches (or approximately 30.5 to 254 mm). In some embodiments, top portion 320 has a radius R2 between approximately 0.020 to 0.300 inches (or approximately 0.5 to 7.6 mm) and a radius R1 between approximately 1.2 to 10 inches (or approximately 30.5 to 254 mm).

FIG. 5A-5C are an illustrative embodiment of a ballistic insert 400 with a concave apex 430. Base 410 is a cylindrically-shaped base. Similar to the top portion 310 discussed in the prior embodiment, top portion 420 is defined by two radii, R1 and R2. Top portion 410 may provide a concave apex 430. Concave apex 430 is disposed on a central axis of the ballistic insert 400. Concave apex 430 is concave-shaped depression provided at the apex of ballistic insert 400. The apex or tip of a cutting element may be point at which the cutting element experiences the highest stresses. By providing a concave apex 430, the stresses may be spread out over the edge of concave apex 430. In conical tipped inserts, the tip may potentially be cracked, broken, or damaged during manufacturing. The ballistic insert 400 has a rounded top portion that avoids this risk of damage during manufacturing.

In an alternate embodiment, further PCD layers may be bonded to grooves or pockets formed on the cutting element. For example, the element may be formed with two or more pockets which may be equidistantly spaced and each of which supports a separate PCD layer. In this regard if PCD layer wears out, the cutting element may be rotated within a pocket of a bit exposing another PCD layer for cutting the earth formations.

FIGS. 6A-6B are an illustrative embodiment of a ballistic insert 500. Ballistic insert 500 provides a base 510 and a top portion 520. Similar to the top portion 310 discussed in the prior embodiment, top portion 520 is defined by two radii, R1 and R2. Further, base 510 provides a rounded bottom 530, which may more evenly distribute stress to a body the ballistic insert 500 is secured in.

In another embodiment, a ballistic insert may provide a material layer bonded to a substrate. The material layer may be a mixture of one or more of PCD, cobalt, carbide, CBN, or any other tough material that is suitable for mining or drilling. In some embodiments, the material layer may be a combination of PCD and catalyst such as cobalt. Further, to prevent potential damage from thermal expansion, said material layer or a portion of the material layer may be leached to remove said catalyst. The substrate may be any suitable material, such as carbide, tungsten carbide, or the like.

The ballistic inserts or inserts described herein may be formed as ballistic substrates using conventional methods. In some embodiments, the ballistic substrates may then be cut or machined to achieve a desired shape using various known methods such as electrical discharge machining (EDM). In some embodiments, the ballistic substrates may be cut or machined to define groove(s) or depression(s) to accommodate inserts of a desired material at particular locations of ballistic inserts. For example, PCD inserts may be placed in grooves position at locations of ballistic insert that experience high stress. In another exemplary embodiment, the substrates are molded with the appropriate grooves or depressions. This may be accomplished by using mold materials which can be easily removed to define the appropriate cut-outs or depressions to accommodate the PCD layer(s). One such mold material may be sand.

In a further exemplary embodiment, the cutting elements may be strategically positioned at different locations on a bit depending on the required impact and abrasion resistance. This allows for the tailoring of the cutting by the bit for the earth formation to be drilled. For example, the cutting elements furthest away from the rotational axis of the bit may have more PCD material at their cutting edge. The cutting elements closer to the rotational axis of the bit may have narrower portions of PCD material occupying the cutting edge. In other words, in an exemplary embodiment, the cutting elements furthest from rotational axis of the bit which travel at a higher speed will require greater abrasion resistance and may be made to include more PCD material at their cutting edge, whereas the cutting elements closer to the rotational axis of the bit which travel at a slower speed will require more impact resistance and less abrasion resistance. Thus, the latter cutting elements will require more ultra hard material at their cutting edge making contact with the earth formations. The amount of PCD material forming the cutting edge of a cutting element may be varied as necessary for the task at hand.

In other exemplary embodiments, inserts incorporating PCD materials may be used in rotary cone bits which are used in drilling earth formations.

The PCD utilized for the ballistic inserts may be substantially free of the problems associated with the use of Period 4 elements or their compounds for the purpose of sintering diamond particles on to a cemented carbide substrate. Naturally available polycrystalline diamond, called Carbonados, is commonly known as “Black Diamond” and can be found in alluvial deposits in the Central African Republic and Brazil. Its natural color is black or gray depending upon the level of impurities such as nitrogen or boron. It is believed that boron and nitrogen atoms can diffuse into the diamond lattice and provide means of bonding diamond crystals together.

Cubic boron Nitride (CBN) is a very hard material synthesized by the same process as industrial diamond. Its hardness is second to diamond and its chemical elements, boron and nitrogen, can diffuse into the diamond crystals and provide bonding not only among diamond crystals but also among CBN and diamond crystals. Coefficient of thermal expansion of CBN is very close to diamond (1.2×10⁻⁶ compared to diamond 1.0×10⁻⁶) and this substantially eliminates local tensile stresses generated due to mismatch of thermal expansion characteristics encountered otherwise in use of group IV and V elements of periodic table or their compounds during the sintering of PCD layer. Since hardness of CBN crystals is much higher than cemented carbide, the resulting hardness of PCD layer synthesized using CBN will be much higher than PCD layer synthesized using Period 4 elements or their compounds.

Although the present invention has been described and illustrated to respect to multiple embodiments thereof, it is to be understood that it is not to be so limited, since changes and modifications may be made therein which are within the full intended scope of this invention as hereinafter claimed.

Experimental Example

The following examples are included to demonstrate particular aspects of the present disclosure. It should be appreciated by those of ordinary skill in the art that the methods described in the examples that follow merely represent illustrative embodiments of the disclosure. Those of ordinary skill in the art should, in light of the present disclosure, appreciate that many changes can be made in the specific embodiments described and still obtain a like or similar result without departing from the spirit and scope of the present disclosure.

Diamond crystals of approximately 4 to 8 micron were mixed with cobalt powder and cemented carbide powder. The weight percent of diamond varied from approximately 40 to 60%, cobalt powder approximately 8 to 15% and cemented carbide powder approximately 25 to 40% by weight. This powder was milled and treated in a vacuum hydrogen system and assembled with a cemented carbide substrate. The inner layer has substantially less amount of diamond crystal. Both layers were assembled with a cemented carbide substrate. The assembly was subjected to a pressure exceeding 88 KBar at temperatures of more than 1400° C. for 10 minutes. The resulting mass was removed and ground to a precise dimensions.

A steel body of suitable geometry was used to braze the ballistic cutting insert described above. In particular, a steel body commonly used in mining and road applications was utilized. A carbide sleeve of conical shape was used to envelop the outer steel body for the purpose of protecting it from erosion. The cemented carbide sleeve was bonded to the steel body by means of a high strength epoxy.

Implementations described herein are included to demonstrate particular aspects of the present disclosure. It should be appreciated by those of skill in the art that the implementations described herein merely represent exemplary implementation of the disclosure. Those of ordinary skill in the art should, in light of the present disclosure, appreciate that many changes can be made in the specific implementations described and still obtain a like or similar result without departing from the spirit and scope of the present disclosure. From the foregoing description, one of ordinary skill in the art can easily ascertain the essential characteristics of this disclosure, and without departing from the spirit and scope thereof, can make various changes and modifications to adapt the disclosure to various usages and conditions. The implementations described hereinabove are meant to be illustrative only and should not be taken as limiting of the scope of the disclosure. 

What is claimed is:
 1. A cutting element for mining a formation, the cutting element comprising: a ballistic insert that provides a top portion comprising a first section forming a tip of the ballistic insert and a second section below said first section, wherein the first section has a shape characterized by a first radius (R1), the second section has a shape characterized by a second radius (R2), and R1 and R2 have a tangential relationship, and a bottom portion supporting the top portion.
 2. The cutting element of claim 1, further comprising a body providing a recess for receiving said ballistic insert.
 3. The cutting element of claim 2, further comprising a sleeve that is positioned on the body, wherein the sleeve protects the body from erosion.
 4. The cutting element of claim 2, wherein the body is steel.
 5. The cutting element of claim 1, wherein the ballistic insert is solid body comprising a mixture of polycrystalline diamond (PCD) and cubic boron nitride (CBN).
 6. The cutting element of claim 1, wherein the ballistic insert is polycrystalline diamond (PCD), cubic boron nitride (CBN), cobalt, carbide, tungsten, or a combination thereof.
 7. The cutting element of claim 1, wherein the top portion of said ballistic insert is polycrystalline diamond (PCD), cubic boron nitride (CBN), or a combination thereof.
 8. The cutting element of claim 1, wherein the bottom portion of said ballistic insert is a carbide substrate.
 9. The cutting element of claim 3, wherein the sleeve is a carbide.
 10. The cutting element of claim 1, wherein a tip of the top portion of said ballistic insert provides a concave apex.
 11. The cutting element of claim 1, wherein R2 is between 0.02 to 0.30 inches or 0.5 to 7.6 mm.
 12. The cutting element of claim 1, wherein R1 is between 1.2 to 10 inches or 30.5 to 254 mm.
 13. The cutting element of claim 1, wherein a ratio of R1 to R2 (R1/R2) is equal to or greater than
 18. 14. The cutting element of claim 1, wherein the ballistic insert provides one or more depressions for receiving an insert.
 15. The cutting element of claim 2, wherein the body provides one or more openings for receiving an insert.
 16. The cutting element of claim 1, wherein a height of said top portion is equal to or greater than 1 inch. 